1. Field of the Invention
This invention generally relates to a switch, and in particular, relates to a micro machine switch having a movable portion.
2. Description of the Related Art
A switch for switching a high-frequency signal has been used widely. For example, a GaAs semiconductor switch is used in a switching circuit for switching between sending and receiving circuits such as a cellular phone, because the GaAs semiconductor switch has high responsivity. However, with respect to the GaAs substrate switch, an electrical loss in “ON” state is large and isolation in “OFF” state is low. And so, a MEMS (Micro Electro Mechanical System) switch manufactured with a micro machine processing technology using a Si substrate is noted. In the MEMS switch (Micro Machine Switch), the electrical loss in “ON” state is small and the isolation in “OFF” state is large, because an electrical contact is turned on and off directly. Japanese Patent Application Publication No. 2005-243576 discloses the MEMS switch.
However, the isolation of the MEMS switch in the “OFF” state is degraded when the operation frequency is high. For example, there is a demand for reducing the isolation level in the “OFF” state less than −30 dB. However, there is a case where the isolation level in “OFF” state is more than −30 dB in the MEMS switch using a high frequency wave. A requirement affecting the isolation level in “OFF” state has not been examined with respect to the MEMS switch.